1. Field of the Invention
The present invention relates to a vehicle navigation system. In particular, the present invention relates to a vehicle navigation system suitable for a compact vehicle in which a large display space is difficult to ensure.
2. Description of Background Art
Navigation systems in which the current location of a vehicle is displayed on a map by combining a position detection device (GPS: Global Positioning System) utilizing satellite radio waves and map information to guide the vehicle to a destination, are being widely used.
Heretofore, vehicle navigation systems have been mainly developed for four-wheel cars. However, in recent years, mounting vehicle navigation systems on compact vehicles, such as motorcycles and buggy cars for rough terrains, is also being studied. However, in known navigation systems, a display screen has become large as a result of the attempt to provide a large amount of information to a driver. In compact vehicles including motorcycles, it has been difficult to ensure a mounting space for a display panel within the sight of a driver.
In order to solve such a technical problem, a vehicle navigation system in which guidance information necessary for a driver can be provided in a small display space has been described in (Japanese Unexamined Patent Publication No. 2002-350144).
FIG. 10 is a view showing the configuration of a display panel of the above-described known vehicle navigation system. The display panel includes a speed display area 61, a positioning status display area 62 for displaying the positioning status of a GPS, a multiplex display area 63 which functions as an odometer and a trip meter and in which the number of the way point (WP: relay point) currently selected, the distance to the WP, and the like are displayed, and a direction display area 64 for displaying the direction of the WP or the final destination with an arrow.
Below the display panel 6, a “MODE” switch 65 for switching the operation mode of the navigation system, a “WPT” switch 66 for newly registering the current position as a WP, and an “INC” switch 67a and a “DEC” switch 67b for selecting a WP, are provided.
FIG. 11 is a view showing a display example of the display panel 6 when a vehicle is running. In the speed display area 61, a speed of “28” miles per hour is displayed. In the positioning status display area 62, positioning status is displayed. In the multiplexed display area 63, the identification number “1” of a way point WP and “1.23 (miles),” which is the distance from the current position to the way point WP1, are displayed. In the direction display area 64, an arrow indicating the direction of a destination or a WP is displayed.
The above-described known navigation system can recognize the position and the traveling direction thereof based on GPS radio waves, but cannot recognize the orientation thereof, i.e., the orientation of the display panel 6. More specifically, the navigation system cannot recognize whether the display panel 6 is oriented to north as in FIG. 12(a) or to south as in FIG. 12(b). Moreover, the navigation system shows the direction of a destination with an arrow by regarding the front direction of the display panel 6 as the traveling direction. Accordingly, when a vehicle moves in the direction opposite to a target direction, an arrow indicating the back direction of the display panel 6 is displayed in the direction display area 64 of the display panel 6 regardless of the orientation of the display panel 6.
Consequently, there has been the following technical problem: if the vehicle 100 moves forward while facing the direction opposite to the target direction T as shown in FIG. 13(a), a correct arrow directed in the target direction T is displayed in the direction display area 64 of the display panel 6, but, if the vehicle moves backward while facing the target direction, an arrow directed in the direction opposite to the target direction T is displayed as shown in FIG. 13(b).
Note that Japanese Unexamined Utility Model Publication No. Sho 62(1987)-156821 discloses a technology in which when a vehicle is moving backward, 180° is added to orientation information given by an orientation sensor, thereby properly showing a vehicle swept path even during backward motion.
However, in the above-described known navigation system, only the vehicle swept path is displayed, but it is impossible to properly display direction guide information, such as the orientation of the traveling direction and a target direction, for guiding a driver to a predetermined direction, when the vehicle is moving backward.